Why Raptors?
The raptors trade Jose's expiring contract and in return get their pick back and a serviceable backup in Williams. In the end it's like we traded Jose for Lowry and Williams.

Why Utah?
Their front court is way to crowded. Utah has great talent with favours and kanter but they can't get any minutes behind Jefferson and Milsap, and it's been rumoured for a while one of them would be traded. Jefferson can also walk so they atleast get something for him. A few weeks ago their were talks of buying out bell but then decided to look for trade destinations instead. So they get rid of bell without paying him 3 mil. They get Kevin Martin who is a nice 2 guard giving them a nice backcourt aswell. They get Jose instead of Williams who is a clear upgrade IMO. With Martin and Jose's contracts coming up at the end of the season it frees up 22 million dollars(which would leave them with 16 million in cap space I believe) for free agency. They also receive Perkins who would be a nice backup or mentor for kanter until he gets good enough. The picks give them a nice setup for the future, since Dallas will struggle with dirk out for a bit, and Sacramento and Charlotte almost guaranteed to have high 2nd round picks.

Why OKC?
They get an allstar center in Jefferson it's pretty simple. They get rid Perkins large contract, and give lamb a chance to start at the 2. They gain a solid 3 point shooter and mentor in bell. Westbrook Durant and Jefferson would be unstoppable.